open outcry (idea)

Open outcry is the system of floor trading historically used in stock exchanges, although most of the major exchanges in the world markets are now electronic.

Technically, the meaning of open outcry is that your bid or offer is good 'while the breath is warm'. What this actually means is that each trader on the exchange will shout out what trade he is trying to execute. He is not able to just shout it once and assume everyone has heard him, he must keep shouting. If he stops shouting, it is assumed that he no longer wishes to trade at that price level.

Everyone around him is also shouting, resulting in a lot of noise, and not much clarity.
The consequence of this is that not only do traders have to shout continuously what trades they are trying to fill, they must also hand signal their trades, in case a trader in the distance cannot hear clearly. The hands and the mouth must say the same thing. Traders cannot just trade with hand signals, and they must take examinations to comply with he requirements of the respective exchanges.